Boston’s new bus-only lanes are an improvement. But who will pay for them?

A bus used a dedicated lane on Washington in Boston on Tuesday.Craig F. Walker/Globe Staff

Pete Seweryn’s commute between Roslindale Square and the Orange Line station at Forest Hills became noticeably faster last spring, when Boston banned parking on the inbound side of Washington Street during the morning rush and replaced it with a dedicated space for MBTA buses.

“I’ve noticed a big difference. It’s probably shaved off a good 15 or 20 minutes,” Seweryn said. “Before, you’d just creep along and it would take forever, so it’s definitely a big improvement.”

Hailed by both the city and the Massachusetts Bay Transportation Authority as a simple but significant transit improvement that can be replicated across the region, the Roslindale bus lane has been a boon to thousands of daily bus riders in southwest Boston who now cruise past stalled auto traffic each morning.

But it has also raised a tough question: Who is responsible for managing these additions to the roads — the state-run transit agency that owns the buses or the city that owns the streets?

Now, as Boston plans the next phase of bus lanes across the city, the Walsh administration is lobbying the T to shoulder more of the financial and operational responsibilities that are typically borne by a city or town, such as paying for the signs and coats of paint that delineate bus lanes.

“It’s great to have all these bus lanes, but we have to figure out how they’re going to be maintained,” Boston transportation planner Vineet Gupta said at a meeting of the MBTA’s board of directors in December. “Who exactly is going to take on these shared responsibilities?”

It’s unclear what, exactly, Boston wants from the state. The Boston Transportation Department declined to comment beyond Gupta’s remarks. Spokeswoman Tracey Ganiatsos said the city has spent more than $140,000 on the Roslindale lane, most of which was to mark off that section of the street with paint, with a smaller amount for staff time to set up the lane and oversee it at the very beginning.

The MBTA has handled some costs as well. The T paid to design the lane, and spokesman Joe Pesaturo said the agency’s transit police help enforce parking rules while on patrol.

MBTA deputy general manager Jeff Gonneville steered clear of publicly engaging Boston officials on the issue, saying only that the T is “working very closely with the city” to reach a solution.

Boston City Councilor Michelle Wu said she expects the city to absorb most of the costs and planning for bus lanes, which would also give Boston more say in how they are implemented.

“I assume that the city would have responsibility over maintenance, just as they maintain every other part of our city infrastructure,” she said. “The last thing I’d want to see is the MBTA holding off on the lanes, not based on routing but on availability of paint.”

But, she added, it may make sense for the state to chip in some since Boston already pays more to the T than any other city or town in an annual assessment — about $85 million in the most recent year.

Activists see this as the kind of typical Boston-area jurisdictional dispute that threatens to slow adoption of a transportation improvement at a critical time.

“Every day that lines of responsibility aren’t sorted out is another day that thousands of people sit in traffic on their buses,” said Stacy Thompson, director of the Livable Streets Alliance, which advocates for changes to street design. “For people, that’s lost time at work or with their kids.”

Bus lanes are enjoying a kind of moment in public policy as elected officials, including the administrations of Governor Charlie Baker and Boston Mayor Martin J. Walsh, are celebrating them as a simple, low-cost solution to the gridlock slowing Greater Boston’s streets. They’ve also recently been deployed in communities including Cambridge, Watertown, and Arlington.

In a long-awaited report issued in December, a commission appointed by Baker stressed bus lanes as a key component of statewide transportation planning, and the governor himself championed them as highly efficient because buses carry so many more passengers than cars. Meanwhile, the Walsh administration has said it is considering new bus lanes to run between Allston and Brighton, Mattapan and Longwood Medical Center, and North and South stations.

Everett in 2016 became the first city in the region to eliminate parking for a bus lane and has since installed traffic lights that give T vehicles priority at intersections and high-level platforms at select stops.

“The city owns the infrastructure. We own the road, we own the traffic signals. That responsibility falls on us,” said Everett transportation planner Jay Monty. “It’s important that cities and towns have a partnership with the MBTA and have skin in the game.”

Everett’s various improvements cost about $1 million. Some money, however, did come from state programs for street improvements and private grants from the Barr Foundation. But Everett had to seek out those funds, Monty said.

Transit advocates don’t expect the unanswered question of control to derail Boston’s existing bus lane in Roslindale. And Boston officials, if anything, seem to be embracing the concept. The Walsh administration plans to hire the city’s first-ever transit director to work directly with the T on planning and implementing bus lanes, as well as other staffers to monitor them on a daily basis. City officials said that they expect to discuss the issue with new MBTA general manager Steve Poftak — whose appointment was praised by Walsh — who started the job this week.

Mary Skelton Roberts, codirector of climate issues at the Barr Foundation, which has issued grants to cities for bus improvements, has pushed for BRT, or “bus rapid transit,” lines, where buses are separated from street traffic by concrete dividers and have bigger stops with raised platforms to ease boarding as in the subway system.

“The conversation about who pays for paint feels petty, truthfully,” Roberts said. “It’s the wrong conversation. Paint should not be the thing that gets in the way if we want BRT.”

Roberts said Boston and the state should sign an agreement that clearly states each party’s responsibilities for bus improvements.

Monty, the planner in Everett, said there is a “valid” debate over whether the state should take a larger role in financing bus lanes. He noted that many roads in Greater Boston are owned by the state government — including the Tobin Bridge, where crowded buses from Chelsea often struggle in traffic.

He suggested the state could add bus lanes on stretches of state highway that have high transit ridership. Patrick Marvin, a state Department of Transportation spokesman, said officials have “had informal discussions with a variety of stakeholders” about highway bus lanes, but that there are no plans underway.